Explanation/Reference:

To make changes available to all administrators, and to unlock the objects and rules that are being edited, the administrator must publish the session.
To make your changes available to other administrators, and to save the database before installing a policy, you must publish the session. When you publish a session, a new database version is created.
When you select Install Policy, you are prompted to publish all unpublished changes. You cannot install a policy if the included changes are not published.
Reference: https://sc1.checkpoint.com/documents/R80/CP_R80_SecMGMT/html_frameset.htm?
topic=documents/R80/CP_R80_SecMGMT/126197

Identity Sharing
Best Practice - In environments that use many Security Gateways and AD Query, we recommend that you set only one Security Gateway to acquire identities from a given Active Directory domain controller for each physical site. If more than one Security Gateway gets identities from the same AD server, the AD server can become overloaded with WMI queries.
Set these options on the Identity Awareness > Identity Sharing page of the Security Gateway object:
* One Security Gateway to share identities with other Security Gateways. This is the Security Gateway that gets identities from a given domain controller.
* All other Security Gateways to get identities from the Security Gateway that acquires identities from the given domain controller.
Reference:
https://sc1.checkpoint.com/documents/R80.10/WebAdminGuides/EN/
CP_R80.10_IdentityAwareness_AdminGuide/html_frameset.htm?topic=documents/R80.10/WebAdminGuides/ EN/CP_R80.10_IdentityAwareness_AdminGuide/63005